Many youth with the most serious mental health problems resulting from violence exposure and maltreatment never receive mental health services [MHS].8,11 These youth are disproportionately found in juvenile delinquent populations where 67% - 75% have impairing psychiatric disorders, 20% have severe mental disorders and more than 1/3 need ongoing clinical MHS care- a figure twice the rate of the general adolescent population.7-10-12 Girls are the most vulnerable, understudied and underserved but fastest growing delinquent subgroup, with data strongly suggesting they have the most serious MHS needs: 75-95% have histories of child maltreatment, 95-100% have poly-trauma histories of violence exposure, sexual assault and child maltreatment, up to 50% have current Post Traumatic Stress Disorder [PTSD] and substance and alcohol use disorders [SAUD] and they have higher rates of PTSD and suicidality than delinquent boys.7,10,12,26-28 However there are few, if any, rigorously tested interventions available in the juvenile justice system [JJS] for youth with these comorbid problems. Our primary aim in this proposed study is to evaluate the efficacy of Seeking Safety [SS], an intervention for concurrently treating comorbid PTSD and SAUD that also addresses self harm and negative affect regulation, for female delinquents. This study lays the groundwork for developing a model for importing evidence based treatment [EBT] to high-risk youth who gain the attention of the JJS. We will recruit 250 female delinquents, 13 to 18 years old, with comorbid PTSD and SAUD through the San Diego Probation Department's Girls' Rehabilitation Facility. Our primary aims are to 1) use a randomized control trial design to determine the efficacy of an 8-week, 24 session manualized PTSD/SAUD intervention, 13 compared to the 'treatment as usual' [TAU] (8-week, 24 sessions) provided by the Probation Department for SAUD problems and 2) determine if cognitive factors (verbal skills, executive function) are related to treatment outcomes for SS and TAU. Our secondary aims are to 1) evaluate possible modifications to the SS treatment for improving services to the subject population and 2) use this study as a model for importing EBTs to other high-risk youth in Child Welfare and the JJS by partnering with (a) UC San Diego Comprehensive Research Center in Health Disparities to determine the best approach for fostering collaborative relationships within the alliance of San Diego's community clinics and identify funding streams to provide community-based services for a larger high- risk youth population and (b) Center for Criminality & Addiction Research, Training & Application to learn how to disseminate data about EBTs for youth in JJS across the nation and explore strategies to train correctional officers to work more effectively with traumatized and SAUD youth. With unprecedented support and access through the San Diego County Juvenile Court and Probation Department and a currently embedded multi- disciplinary, translational research program (spanning neurocognitive, psychiatric, imaging, genetics research), we are in a unique position to implement this proposed study that bears far reaching policy implications.